Interior decorative mouldings, such as crown mouldings, door and window casings, chair rails, baseboards, etc., are commonly used in the construction industry, typically having a flat surface on one side at least, and a decorative surface on the exposed other side. The flat side or sides are used for mounting to an interior wall surface.
The visually appealing decorative surface is usually formed in three dimensions with the moulding often having a uniform cross-sectional profile. A uniform cross-sectional profile is the simplest moulding to manufacture either of wood by milling the decorative surfaces, or in the case of extruded plastic moulding by extruding through a uniform profile die. Wood mouldings are commonly used, however the costs are becoming unacceptably high due to the labour intensive nature of the milling process and the gradual depletion of suitable forest wood stocks. Wood moulding typically must be clear of knots and must be of suitable consistency to produce a smooth finish surface. Wood mouldings tend to shrink and may crack or chip during handling and installation. Although, wood mouldings are in North America, the most common type of mouldings used, other less expensive alternatives are becoming popular.
Solid plastic and extruded polystyrene mouldings are also commonly available, however, with their own problems and costs associated. In general, extruded plastic mouldings are not preferred over wood mouldings due to the inability to finish joints properly, potentially toxic fumes which are produced during fires, and the fact that there is very little comparative cost advantage in using plastic mouldings.
Traditional construction methods include preparing solid plaster mouldings and this decorative style is regaining popularity. Complex moulded shapes can be produced with relative ease and improved safety during a fire is a distinct advantage gained through use of a solid plaster moulding. During Victorian times relatively large crown mouldings for example, were fairly common in homes or public buildings. To produce this traditional product, a prepared rubber mould is filled with a liquid plaster mixture to form moulding components of four to six foot length. Longer components are prohibitively heavy and are prone to crack when handled. Solid plaster mouldings are installed on site and painted like the adjacent wall and ceiling surfaces. Solid plaster of course, suffers from handling during installation and chips easily. A relatively high degree of skill is necessary to produce the rubber moulds and to install the moulding correctly without damaging the decorative surface. To provide additional strength and to resist cracking, the plaster mixture in older construction methods would be combined with horsehair, rope fibers or other natural fibers as reinforcement. Modern plastic fibers or fiberglass, Teflon, etc., can also be added to the plaster mixture for reinforcement.
It will be appreciated however, that the manufacture, handling and installation of traditional solid plaster moulding involves significant expense, skilled labour and expertise. Mass production of solid plaster mouldings has not occurred due to the high relative costs, and the inherent risk of damage during shipping and installation. Custom made solid plaster mouldings remain a viable option in historic renovation for example, or in building custom homes where a specific moulding must be matched or produced.
A significant advantage of solid plaster mouldings over wooden mouldings, plastic mouldings or polystyrene extrusions is in meeting fire regulations. High-rise condominiums or hotels, convention centers, theatres, or other high density buildings must meet higher fire codes standards than a low rise low density building or residence. Architects or interior designers may desire use of decorative mouldings in such buildings, however, to comply with fire regulations the mouldings must be coated with special flame spread resistant paints. In the case of wood mouldings, the wood itself adds to the flammable fire load within a building undesirably and extruded polystyrene or plastic mouldings may expose occupants to the risk of toxic fumes during combustion.
Fire codes generally specify the coating of mouldings or flammable materials with flame spread resistant paints or require that mouldings be coated with gypsum plaster. Wood and plastic mouldings can be coated with gypsum plaster by spraying for example. However, this procedure is also labour intensive and requires high level of skill. In the preparation of mouldings for picture frames for example, it is very common to coat wooden mouldings with plaster for decorative effects. This procedure however, involves high labour costs and is generally considered unsuitable for high volume building construction.
It is an object of the present invention therefore to produce a gypsum coated interior moulding which is low in cost and suitable for mass production.
It is a further object of the present invention to produce a light weight interior moulding which is gypsum coated in a manner such that special handling and installation methods are not required since the gypsum coating remains flexible and intact during handling and installation.
It is a further object of the invention to provide a light weight interior moulding which is of a weight such that the moulding can be installed with adhesives, and preferably with liquid gypsum compound as an adhesive, without mechanical fasteners or nails to simplify installation and to reduce the level of skill involved.
It is a further object of the invention to provide a gypsum coated light weight interior moulding secured to plaster walls and ceilings with gypsum compound as an adhesive to maintain the fire resistant properties of the gypsum coating and gypsum adhesive.